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Comment by elandybarr | Hacker News Reader

Failing to use join is a big one.

I have seen countless instances of people writing the logic to output commas in between items (like for CSV export) that they want to concatenate into a string.

    header_line = ','.join( header for header in headers )
    csv_line    = ','.join( str(dataset[key]) for key in dataset.keys() )

Example for a case of a dictionary mapping a string to a bunch of numbers.

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Proper Python would use the csv module for this operation, as your CSV export would break if `header` or `dataset[key]` contains a comma.

Yeah. This was a special case for a one line CSV that was requested by my client. It was a dictionary with a bunch of single measurements.

Any reason not to do the first one more compactly?

     ','.join(headers)

Oops. Good catch!

You should just use dataset.values() (or itervalues if you're using Python 2) instead of iterating over the keys, and then looking them up.

You're relying on dataset.keys() being in the same order as headers. Really, you should use the csv module, even for one-line CSV files.

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